look at these pictures we found on the website for the daily cal when the fire was al full bore between midnight and 2 a.m. at one point the firefighters were inside, the second story was collapsing on them. they had to get out and fight it from the outside. i'm here with deputy fire chief. tell me about that moment when you started to realize that the structure's integrity was being compromised. >> so when the firefighters were inside the outside incident commander was evaluating the structure and saw the heavy amount of flames that were shooting out of the building and that's when they realized that there was going to be a collapse of the second story of the roof structure. so we went defensive spreading the water from the top of our ladder pipe in from the outside into the windows. that's what we call a defensive fire. >> reporter: when you're looking for hot spots, there's a lot of voids you say that hot spots could be hiding. >> with the collapse of the structure, the second floor, it's creating void spots that we can't get to the fire. so there's small hidden hotspots that we're t